Functionalized sea urchin-like MnO2 with chitosan to load CaCo layered double hydroxides for advanced catalytic oxidation of antibiotics through activation of peroxymonosulfate

Novel composite catalysts based on the functionalization of sea urchin-like MnO2 with chitosan (CS) to load CaCo layered double hydroxides were prepared by a simple hydrothermal method, and the physicochemical properties of the resulting MnO2@CS-CaCo LDHs were analyzed by various characterization methods. Then advanced oxidation processes (AOPs) were constructed based on MnO2@CS-CaCo LDHs through activation of peroxymonosulfate (PMS) to degrade ciprofloxacin (CIP), norfloxacin (NOR) and sulfamethoxazole (SMX) in water. Sea urchin-like MnO2 modified by CS created a unique interface and a variety of active functional groups for the loading of CaCo LDHs where MnO2 particles were uniformly attached to the surface of CaCo LDHs. The results showed that the MnO2@CS-CaCo LDHs composites had excellent catalytic performances compared with monomeric MnO2, MnO2@CS and CaCo LDHs, and the enhanced catalytic performances were mainly due to the synergistic effects between LDHs, CS and MnO2. Under optimal experimental conditions, the removal efficiencies of CIP and NOR reached up to 96.45 % and 96.58 % within 20 min, respectively, and the removal of SMX was 93.12 % within 30 min. Quenching experiments demonstrated that 1O2 was the main active oxygen species for catalytic degradation through a non-radical pathway. In addition, the degradation efficiency of NOR was still as high as 93.78 % after the 10th cycle of degradation experiments, indicating that the composite catalysts had excellent reproducibility and stability. Finally, the activation mechanisms of MnO2@CS-CaCo LDHs/PMS and degradation pathways of SMX were proposed. The catalytic performances of MnO2@CS-CaCo LDHs/PMS for removal of three drugs in actual water bodies were further evaluated their practical application ability. [Display omitted] •MnO2@CS-CaCo LDHs as an effective PMS activation catalyst was prepared.•MnO2@CS-CaCo LDHs+PMS system degraded up to 100 % of the pollutants at low concentrations in 10 min.•MnO2@CS-CaCo LDHs had very excellent reusability and high stability.•MnO2@CS-CaCo LDHs+PMS system was characterized by low sensitivity to changes in environmental media.•MnO2@CS-CaCo LDHs+PMS system exhibited good practical application.